CN105765086B

CN105765086B - Annealing furnace and method for annealing steel strand

Info

Publication number: CN105765086B
Application number: CN201480063241.9A
Authority: CN
Inventors: 托马斯·弗罗伯泽; 克里斯托弗·赫德瓦尔
Original assignee: Sandvik Materials Technology Deutschland GmbH
Current assignee: Heruimai Co ltd
Priority date: 2013-12-19
Filing date: 2014-12-10
Publication date: 2021-03-30
Anticipated expiration: 2034-12-10
Also published as: EP3084015A2; EP3084015B1; KR102360743B1; WO2015091138A3; KR20160100960A; WO2015091138A2; JP2017508872A; JP2019206763A; CN105765086A; US20160326609A1; DE102013114578A1; ES2734358T3; JP6860344B2; US10400302B2

Abstract

The invention relates to an annealing furnace (1) for annealing steel strands (2), comprising a first heating device (9) for heating the strands (2) during operation of the annealing furnace (1), and comprising a transport device (4, 5,6, 7) for the strands (2), which is designed to advance the strands (2) through the annealing furnace (1) in a transport direction (3) during operation of the annealing furnace (1). The annealing furnace (1) further comprises a first cooling device (13) for cooling an outer surface (17) of the strand (2) in the transport direction (3) downstream of the first heating device (9), the first cooling device (13) having a gas guide (16), wherein the gas guide (16) is arranged such that during operation of the annealing furnace (1) gas flows along the outer surface (17) of the strand (2) in order to cool the strand (2).

Description

Annealing furnace and method for annealing steel strand

Technical Field

The invention relates to an annealing furnace for annealing steel strands, using a first heating device for heating the strands in the annealing furnace and a transport device for the strands, which transport device is arranged such that the strands are advanced through the annealing furnace in a transport direction during operation of the annealing furnace.

The invention also relates to a method for annealing steel strands in an annealing furnace, comprising the following steps: the strand is heated in a first heating device, and the strand is transported through the annealing furnace in a transport direction using a transport device for the strand.

Background

Many workpieces must be tempered after their actual production, for example by cold forming or hot forming, so that the workpiece achieves the desired material properties, or so that those material properties which are lost as a result of deformation are restored.

In particular, stainless steel tubes are annealed after cold pilger rolling or cold drawing in order to increase the ductility of the material.

In order to ensure maximum throughput, it is preferred that the tempering of the work pieces is performed in a belt furnace, wherein during the tempering the work pieces are actively advanced through the belt furnace.

In comparison with these known annealing furnaces, the present invention is concerned with the problem of providing an annealing furnace which allows a more precise adaptation and improvement of the material properties of the finished workpiece as required.

Disclosure of Invention

This problem is solved by means of an annealing furnace for steel strands, comprising a first heating device for heating the strands in the annealing furnace and a transport device for the strands, which transport device is arranged such that the strands are transported through the annealing furnace in a transport direction, and, after the first heating device, the annealing furnace further comprises a first cooling device for cooling the outer surfaces of the strands, which cooling device has a gas guide, wherein the gas guide is arranged such that, during operation of the annealing furnace, gas can be guided along the outer surfaces of the strands to cool the strands.

It has been found that not only the temperature at which the strand is annealed and the time for which the strand is annealed, but also the cooling process after annealing, are important for the material properties of the steel strand obtained after the annealing process. The annealing furnace according to the invention therefore provides the option of purposefully cooling the strand after heating it in the heating device of the annealing furnace.

Within the scope of the present application, the steel strand is, for example, an elongated oval profile, a rod or a tube.

The steel strand, which is preferably made of stainless steel, is in particular a steel tube which is reduced, i.e. deformed, by cold pilger rolling or cold drawing. Thus, embodiments of the invention can be realized in a case where the lehr is part of an integrated production line having a pilger cold pilger mill and a lehr arranged downstream. Alternatively, the broaching machine may be integrated in the production line.

The central element of the annealing furnace is a first heating device that facilitates heating the strand to a desired annealing temperature. Thus, it is advantageous if in an embodiment of the invention the heating device is arranged to heat the strand to a temperature in the range from 300 ℃ to 500 ℃, preferably from 350 ℃ to 450 ℃, and particularly preferably 400 ℃.

Although a number of embodiments can be foreseen in such a heating device, an embodiment wherein the first heating device comprises an induction coil for induction heating of the twisted wire is advantageous. By means of such an induction heating device, the strand material can be heated very quickly in a concentrated manner over a short length range.

In an embodiment of the invention, the induction coil is arranged and designed such that the strand passes through the induction coil in the annealing furnace. Here, the stranded wire and the induction coil must preferably be arranged concentrically, in particular when the stranded wire is a cylindrical element, such as a rod or a tube having a circular cross-section.

In an embodiment of the invention, the first heating device comprises a hollow glass cylinder which extends between the strand and the induction coil during operation of the lehr and preferably concentrically surrounds the strand.

Within the scope of the invention, the transport device is essentially any suitable mechanical device capable of advancing the strand to be annealed through the annealing furnace.

In an embodiment, the transport means comprises at least one pair of motor-driven drive rollers arranged such that the drive rollers engage the strands during operation of the annealing furnace and the strands extend between the drive rollers. In one embodiment, the annealing furnace comprises two pairs of motor-driven drive rollers, wherein a first pair of drive rollers is located in front of the first heating device in the transport direction and a second pair of drive rollers is located behind the first heating device.

The first cooling device according to the invention has the advantage that the strand is cooled efficiently and quickly, on the basis of a gas flow (gas current) being guided over the outer surface of the strand.

In an embodiment of the invention, the gas guide comprises a housing surrounding the strand (preferably arranged concentrically with the strand) during operation of the annealing furnace, wherein the housing has a gas inlet and a gas outlet for the gas.

To prevent gas leakage, the enclosure has a seal at the front end and a seal at the rear end to seal the tube to the strands during operation of the annealing furnace.

In an embodiment of the invention, the gas inlet of the gas guide is in fluid communication with a gas holder, wherein the gas holder preferably contains hydrogen during operation of the annealing furnace, so that the outer surface of the strand can be cooled with gas, in particular hydrogen.

The hydrogen cooling simultaneously allows chemical reduction of the steel on the outer surface of the twisted pair.

In an embodiment of the invention, the gas outlet in the strand transport device is arranged in front of the gas inlet, so that the gas flows through the strand counter to the transport direction during operation of the annealing furnace. This improves the efficiency of the gas cooling.

In a further embodiment of the annealing furnace, there is a second cooling device for cooling the outer surface of the strand, wherein the second cooling device comprises a contact element which can be engaged with the strand during operation of the annealing furnace, in order to establish a thermal contact between the strand and the contact element. In this way, heat can be efficiently removed from the stranded wire by heat conduction.

For this purpose, it is advantageous if the second cooling device for cooling the outer surface of the strand comprises a pneumatic or hydraulic device which is designed and arranged such that it remains engaged with the strand during operation of the annealing furnace.

It is particularly advantageous if the second cooling device comprises a plurality of contact elements, for example four contact elements, which are pressed against the strand in opposite directions during operation of the annealing furnace.

In one embodiment of the invention, the contact element comprises graphite. Graphite has the advantage of both high thermal conductivity and good tribological properties.

In order to enable efficient heat dissipation from the strands through the contact elements, in one embodiment the second cooling means comprises a fluid cooling means. Such a cooling system is arranged such that the system dissipates heat transferred from the strands to the graphite elements during operation of the annealing furnace.

In an embodiment of the invention, the contact element of the second cooling device for cooling the outer surface of the strand is arranged in the first cooling device for cooling the outer surface of the strand. It is advantageous if the contact element is arranged in the housing of the gas guide of the first cooling device for cooling the outer surface of the strand.

The combination of the first and second cooling means for cooling the outer surface of the strand enables an efficient and thus fast cooling for the quenching of the previously red hot steel pipe. This quench cooling is also known as quenching.

In another embodiment, the annealing furnace comprises a third cooling device for cooling the outer surface of the strand, the third cooling device comprising a housing with fluid cooling. Preferably, the third cooling device is arranged downstream of the first cooling device in the transport direction and surrounds the strand during operation of the annealing furnace. In this cooling device, the strand is further cooled after quenching in the first cooling device or in the first and second cooling devices, wherein the cooling effect is based on the fact that: the housing of the third cooling device has a lower temperature than the strands running inside the housing due to the fluid cooling.

According to an embodiment of the invention, a third cooling device for cooling the outer surface of the strand may additionally or alternatively be provided together with the second cooling device for cooling the outer surface of the strand.

Another embodiment of the annealing furnace comprises a fourth cooling device for cooling the outer surface of the strands, the fourth cooling device being arranged such that during operation of the annealing furnace the strands are sprayed with a fluid, preferably with water.

Here, a fourth cooling device can be provided in addition to or instead of the second and/or third cooling device.

In a further embodiment of the invention, the annealing furnace comprises a second heating element downstream of the first heating device in the transport direction of the strand. If the first heating device is, for example, an induction heating device, it proves that: it is advantageous if the second heating device is a conventional heating device with a heating wire operated electrically.

Although the embodiments provided so far are for cooling and rinsing the outer surface of the strands, there is one embodiment of the annealing lehr of the present invention, which includes an annealing lehr for annealing hollow strands having a rinsing device for rinsing the inner surface of the hollow shaft. In this case, the flushing device comprises a gas outlet for flushing the inner surface, which outlet can be connected to one end of the hollow strand, so that gas for flushing the inner surface of the hollow strand can be introduced into the hollow strand from the gas outlet and can flow along the inner surface during operation of the annealing furnace.

Here, an embodiment is advantageous in which the gas outlet is in fluid communication with at least one gas storage vessel (preferably at least one storage vessel for argon or a mixed gas of argon and hydrogen), wherein during operation of the annealing furnace, gas is supplied from a gas storage tank.

In one embodiment of the invention, the annealing furnace of the invention is part of a forming system for deforming the already cold-formed strands again, comprising a cold-forming device which is arranged downstream of the annealing furnace in the strand transport direction.

During the production of the strand, in particular of a steel tube made of stainless steel, the deformation of the tube blank into the finished strand can advantageously be carried out sequentially or stepwise in order to achieve the desired material properties of the finished strand. For this purpose, as a first step, the tube blank is reduced by cold forming, in particular by cold pilger rolling or cold drawing. The resulting strand has a significantly increased tensile strength compared to the tube blank, which makes it impossible to cold-deform the strand again. Thus, in one embodiment of the invention, the strand that has been cold-deformed is annealed in an annealing furnace according to an embodiment of the invention and then deformed again in a cold-deformation device.

According to an embodiment of the deformation system according to the invention, the cold deformation device is in particular a cold drawing machine or a drawing bench or a pilger cold pilger mill known from the prior art.

Thus, in one embodiment of the invention, the following alternatives are also possible: the already cold-deformed strand is fed from the cold-rolled pilger system or cold-drawn system directly into the deformation system according to the invention (in-line production), or the already deformed strand can be wound or cut into sections by means of the deformation system according to the invention.

In a further embodiment, a winding device and/or a saw which can be moved in the transport direction of the strands can be arranged downstream of the cold-forming device of the forming plant according to the invention.

Such a saw, which is also movable and is also referred to as a flying saw, is able to divide the strand exiting from the cold-forming device into sections of desired length while the forming process is still running. Alternatively, the strand may be wound or coiled by a coiling device. A suitable winding device is described, for example, in patent application DE 102009045640 Al.

A cleaning device for cleaning the outer surface of the strand may optionally be provided between the cold-forming plant and the sawing and/or winding device. Such cleaning devices are used to remove lubricant residues remaining on the outer surface of the strands from the deformation process. Preferably, the cleaning means is using CO₂Cleaning device for cleaning the outer surface of the stranded wire.

The above problem is also solved by a method for annealing a steel strand in an annealing furnace, comprising the steps of: heating the stranded wire in a first heating device; transporting the stranded wire through the annealing furnace in a transporting direction by a transporting device; after the first heater in the transport direction, the outer surface of the strand is cooled in a first cooling device using a gas guide, wherein the gas flows along the outer surface of the strand with the aid of the gas guide in order to cool the strand.

Such a process of strand annealing is used in particular in embodiments of the invention for producing steel strands, in which a billet (preferably a billet) is cold-deformed into a strand, preferably by cold pilger rolling or cold drawing, before the strand is heated.

The various aspects of the invention have been described so far in terms of an annealing furnace according to the invention, which is also applicable to a corresponding method for annealing strands, and vice versa. To the extent that the inventive method is performed using an annealing furnace according to an embodiment of the invention, the annealing furnace has suitable equipment for this purpose. In particular, however, even embodiments of an annealing furnace for carrying out embodiments of the method described herein are suitable, and the method comprises the steps required for this purpose.

Drawings

Further advantages, features and possibilities of application of the invention will become apparent from the following description of embodiments and the accompanying drawings.

FIG. 1 shows a schematic perspective view of an annealing furnace according to an embodiment of the present invention.

Fig. 2 shows a partial cross-sectional view through two cooling devices of the annealing lehr of fig. 1.

Fig. 3 shows a schematic cross-sectional view through one cooling arrangement of the annealing lehr of fig. 2.

Fig. 4 shows a schematic view of a deformation system according to an embodiment of the invention.

Detailed Description

In fig. 1, an annealing furnace 1 of an embodiment of the present invention is schematically shown. In the meaning of the present application, the stainless steel tube 2 as a strand is annealed at a temperature of 400 ℃ in an annealing furnace 1. To anneal the steel tube, the steel tube 2 is guided through the annealing furnace 1 in the transport direction (this is indicated by arrow 3 in fig. 1). Thus, annealing of the steel pipe 2 continuously occurs in the annealing furnace 1.

According to the present application, there are two pairs of motor-driven

drive rollers

4,5 and 6,7 which function as transport means for transporting the steel tube 2 through the annealing furnace 1. These drive rollers engage the stainless steel tube 2 to be annealed, so that rotation of the

drive rollers

4,5,6,7 causes a translational movement of the steel tube 2 through the annealing furnace 1 in the transport direction 3.

A pair of sets of straightening rolls 8 are also provided in the entry region of the lehr 1, the straightening rolls 8 helping to straighten the cold deformed incoming steel pipe in the X and Y directions of the lehr 1, making the steel pipe substantially straight before being annealed in the lehr.

The proposed embodiment of the annealing furnace 1 comprises two

heating devices

9, 10. According to the present application, the heating device 9 is a first heating device and the heating device 10 is a second heating device. The second heating device 10 comprises two

heating radiators

11, 12.

The first heating device 9 in the transport direction 3 of the annealing furnace 1 is an induction heating device, wherein the steel pipe 2 is heated by using an electric current induced by an induction coil within the steel pipe 2 to be heated.

Such induction heating has the advantage that it heats the steel tube 2 quickly in a very efficient manner, but causes only a very small expansion of the steel tube 2.

The induction coil 30 surrounds the steel tube 2 in a concentric manner, wherein the coil is wound on a hollow glass cylinder extending between several turns of the coil and the steel tube 2.

In the case of the

radiators

11,12, the second heating device is a conventional electrical resistance heater, which is arranged behind the first induction heating device 9 in the transport direction 3 of the steel pipe 2. The insides of the

radiators

11,12 are heated by the heating coils so that the steel pipe 2 is not cooled or hardly cooled on its way from the first induction heating apparatus 9 to the cooling device.

The annealing furnace in the embodiment shown in fig. 1 has a total of four

different cooling devices

13,14,15, 31.

The core element for cooling the annealed steel tube 2, which is located behind the second radiator 12 in the transport direction 3, is a quenching or quenching device which consists of two

cooling devices

13,14 which are integral with one another. According to the application, the two

cooling devices

13,14 are a first and a second cooling device.

The first cooling device 13 is a gas cooling device for cooling the outer surface, i.e. the envelope surface, of the steel pipe 2. The first cooling device 13 uses a hydrogen gas stream for cooling, which flows over the outer surface of the steel pipe 2 and thus cools the steel pipe.

However, there is contact cooling in the second cooling device 14, which provides thermal contact between the steel pipe and the water cooling device to dissipate the heat in the annealed steel pipe 2.

The two

cooling devices

13,14 are shown in detail in the partial sectional view in fig. 2. The gas cooling of the first cooling device 13 consists in the meaning of the present application essentially of a housing 16, which housing 16 as a gas guide concentrically surrounds the steel tube 2 to be cooled. Such a gas guide ensures that the cooling gas is guided over the outer surface 17 of the steel tube 2 to be cooled.

The outer shell 16, which is a gas guide surrounding the steel tube 2 to be cooled, comprises a gas inlet 18 for supplying cooling gas and a gas outlet 19 for discharging gas. During operation of the annealing furnace, the gas inlet 18 is connected to hydrogen (H)₂) The gas storage tank.

The housing 16 of the gas guide has a gas restrictor 20 at its front end and a gas restrictor at its rear end to ensure that as little gas as possible can escape from the gas guide. In the region of the flow restrictor 20, the distance from the housing 16 to the steel tube 2 to be cooled is significantly smaller than the distance between the inner walls of both tube sections 21,22 of the housing 16 and the steel tube 2 to be cooled. The flow resistance of the resulting radial gap between the flow restrictor 20 and the steel pipe 2 to be cooled is therefore significantly higher for the cooling gas than for the pipe sections 21,22 of the housing 16 and the housing flanges 18, 19, so that the gas escapes from the cooling device mainly through the flange 19. In one embodiment, the flow restrictor 20 is made of graphite in order to avoid damaging the steel tube 2 in case the flow restrictor 20 engages the stainless steel tube 2 to be cooled.

The gas inlet 18 of the first cooling device 13 is located behind the gas outlet 19 in the transport direction 3 of the steel tube 2 to be annealed. This promotes the flow of cooling gas on the outer surface 17 of the steel tube 2 opposite to the transport direction 3 during operation of the annealing furnace.

The housing 16 of the gas guide of the first cooling device 13 is not a continuous tube, but consists of three sections (21, 22, 23). The first section 21 is a pipe section 21 concentrically surrounding the steel pipe 2 to be cooled, the pipe section 21 being connected to a flange 18 as a gas inlet. The second section 22 is also configured as a segment concentrically surrounding the steel pipe 2 to be cooled. The second section 22 is in turn connected to a flange as gas outlet 19.

The tubes 21,22 of the outer shell 16 are lined from the inside with a lining 31 made of graphite. The lining 31 prevents damage to the steel pipe 2 to be cooled when the steel pipe 2 is joined to the outer shell 16.

Between the two pipe sections or the pipe sections 21,22 of the gas guide, a further gas guide 23 is present, in which pipe section 23 the second cooling device 14 extends. In this pipe section 23, the gas guide has a substantially cylindrical body 24, the substantially cylindrical body 24 having a much larger inner diameter than the two pipe sections 21,22 of the housing 16. The body 24 is sealed with the other two lengths of tubing 21,22 connected to the gas director. The gas flows through designated passages in the body 24 which extend to the tube 2 to be cooled, or to its outer surface 17.

The contact cooling means of the second cooling means 14 are also arranged within the body 24. The cooling effect of such a contact cooling device is based on four cheek plates (cheeks)25 made of graphite, which cheek plates 25 engage the steel tube 2 to be cooled inside the body 24 and thus establish a thermal contact between the steel tube 2 and the graphite cheek plates 25 for removing heat from the steel tube. The design of the contact element 25 made of graphite has the following advantages: they have a relatively high thermal conductivity and at the same time exhibit a small sliding friction between the steel pipe 2 and the cheek plates 25. The graphite cheek 25 must be hydraulically pressed against the steel tube 2 using a combination of hydraulic cylinders and pistons in order to achieve good thermal contact between the graphite cheek 25 and the steel tube 2.

The cheek plates 25 are worn by friction with the steel pipe 2. However, this wear is automatically compensated by the hydraulic pressure pressing against the cheek plates 25. To facilitate this compensation, the cheeks 25 are designed to be conical in cross section, wherein the four cheeks together do not cover a complete 360 ° ring, but rather a gap is provided between the cheeks 25 in each case. As shown in fig. 3, in a schematic cross-sectional view through the cheek plate 25 and the steel pipe 2, the formed gap 26 can be clearly recognized. Such a clearance not only makes it possible to compensate for wear of the cheeks, but also indicates that the cooling gas can flow through at least along the steel tube 2 in a multi-stage manner.

Returning to fig. 1, the structure of the

downstream cooling devices

15 and 31 will now be described in detail. According to the application, these cooling means 15,31 form a third cooling means 15 and a fourth cooling means 31 for cooling the outer surface 17 of the steel tube 2.

The cooling device 15 comprises two cooling

regulators

27,28 formed by water-cooled pipe sections 29, wherein heat transfer takes place between the steel pipe 2 to be cooled and the cooling pipe sections 29 by means of thermal radiation and convection.

In the last cooling device 31 (so-called water box) in the transport direction 3, the steel pipe 2 is finally sprayed directly with a cooling liquid (here water) which drips and is scraped off the steel pipe with a wiper before the steel pipe leaves the water box.

The annealing furnace in fig. 1 additionally comprises a rinsing device for rinsing the inner surface of the annealed steel tube 2. For this purpose, a gas outlet (not shown) of a gas holder is connected in a sealed manner to the open end of the steel tube 2 to be annealed in front of the annealing furnace 1 in the transport direction 3 of the steel tube 2, so that gas can flow into and through the steel tube.

The embodiment of the invention schematically shown in fig. 4 shows a continuously operating bench 32 for cold forming the steel pipe 2 after the annealing furnace 1. During cold forming of the steel tube 2, the steel tube 2 is reduced by moving it through a drawing die 33The outer diameter of the steel pipe 2. A flying saw 34 is also provided after the broaching machine 32, which moves with the steel pipe 2 in the transport direction 3 of the steel pipe 2, so that the steel pipe 2 can be cut into pipe sections of defined length during drawing of the pipe. In addition, CO is provided between the broaching machine 32 and the flying saw 34₂A cleaning device 35 to clean the outer surface of the steel pipe 2. With the aid of such a cleaning device 35, residual lubricant can be removed from the outer surface of the steel pipe 2. In the sense of the present application, the arrangement of the annealing furnace 1, the bench 32, the cleaning device 35 and the flying saw 34 is designated as a deformation system 36.

For the purposes of this original application, it should be understood that all features will be apparent to those skilled in the art from the following description, drawings and claims, even if they are specifically described only with respect to certain other features, these features can be combined individually and in any combination with other features or groups of features disclosed herein, unless such combinations are explicitly excluded or unless a technical factor renders such combinations impractical or meaningless. Explicit representation of all possible combinations of features described herein has been omitted for brevity and readability of the description only. While the invention has been illustrated and described in detail in the drawings and foregoing description, such statements and description are to be considered illustrative only and not restrictive in scope, as defined by the appended claims. The invention is not limited to the disclosed embodiments.

Variations to the disclosed embodiments will become apparent to those skilled in the art from the following figures, description and appended claims. In the claims, the word "comprising …" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that certain features are recited in mutually different claims does not exclude a combination of certain features. Reference signs in the claims shall not be construed as limiting their scope.

List of reference numerals

1 annealing furnace

2 stainless steel pipe

3 direction of transport

4,5,6,7 drive roller

8 straightening roller component

9 first heating device

10 second heating device

11,12 radiator of a second heating device

13,14,15,31 cooling device

16 housing part of gas guide

17 outer surface of stainless steel pipe 2

18 gas inlet

19 gas outlet

20 sealing element

21,22,23 gas guide housing

24 cylindrical body

25 graphite cheek plate

26 gap

27,28 cooling regulator

29 water-cooled tube section

30 induction coil

31 graphite lining

32 broaching machine

33 drawing die

34 flying saw

35 CO₂Cleaning device

36 deformation system

Claims

1. An annealing furnace (1) for annealing steel strands (2), having:

a first heating device (9), the first heating device (9) being used for heating the stranded wire (2) during the operation of the annealing furnace (1),

a transport device (4, 5,6, 7) for the strand (2), which transport device is adapted to advance the strand (2) through the annealing furnace (1) in a transport direction (3) during operation of the annealing furnace (1),

wherein the annealing furnace (1) comprises a first cooling device (13) in the transport direction (3) downstream of the first heating device (9), the first cooling device (13) having a gas guide (16) for cooling an outer surface (17) of the strand (2), wherein the gas guide (16) is arranged such that gas flows over the outer surface (17) of the strand (2) in order to cool the strand (2) during operation of the annealing furnace (1), wherein the annealing furnace (1) comprises a second cooling device (14) for cooling the outer surface (17) of the strand (2), wherein the second cooling device (14) comprises a contact element (25), the contact element (25) being engageable with the strand (2) during operation of the annealing furnace (1) in order to establish a thermal contact between the strand (2) and the contact element (25), characterized in that the contact element (25) comprises graphite and the gas guide of the first cooling device comprises a housing consisting of three sections, the second cooling device extends in a middle section of the housing, and the contact element consists of four cheeks between which a gap is provided.

2. The annealing furnace (1) according to claim 1, characterized in that a housing (16) of the gas guide surrounds the strand (2) during operation of the annealing furnace (1), wherein the housing (16) has a gas inlet (18) and a gas outlet (19) for the gas.

3. The annealing furnace (1) according to claim 2, characterized in that the enclosure (16) of the gas guide comprises seals (20) at both the front and rear ends, the seals (20) being used to seal the enclosure (16) against the strand (2) during operation of the annealing furnace (1).

4. The annealing furnace (1) according to claim 2 or 3, characterized in that the gas inlet (18) of the gas guide (16) is in fluid communication with a gas tank.

5. The annealing furnace (1) according to any one of claims 2 to 3, characterized in that, in the transport direction (3) of the strand (2), the gas outlet (19) is arranged in front of the gas inlet (18) so that the gas flows through the strand (2) counter to the transport direction (3) during operation of the annealing furnace (1).

6. The annealing furnace (1) according to claim 1, characterized in that the second cooling device (14) for cooling the outer surface (17) of the strand (2) comprises a pneumatic or hydraulic device which is constructed and arranged such that it keeps the contact element (25) engaged with the strand (2) during operation of the annealing furnace (1).

7. The annealing furnace (1) according to any one of claims 1 to 3, characterized in that the second cooling device (14) for cooling the outer surface (17) of the strand (2) comprises a fluid cooling system arranged to dissipate heat transferred from the strand (2) onto the contact elements (25) during operation of the annealing furnace (1).

8. The annealing furnace (1) according to any one of claims 1-3, characterized in that the annealing furnace (1) comprises a third cooling device (15) for cooling the outer surface (17) of the strand (2), the third cooling device (15) comprising a housing with a fluid cooling system, which housing surrounds the strand (2) during operation of the annealing furnace (1).

9. The annealing furnace (1) according to claim 2, characterized in that the enclosure (16) is arranged concentric to the strand (2).

10. Annealing furnace (1) according to claim 4, characterized in that the gas tank contains hydrogen during operation of the annealing furnace (1).

11. A forming system (36) for deforming cold-formed strands (2), comprising an annealing furnace (1) according to any one of the preceding claims, and comprising a cold-forming device.

12. The forming system (36) according to claim 11, characterized in that the cold-forming device is a drawing device (32) arranged behind the annealing furnace (1) in the transport direction (3) of the strand (2).

13. The forming system (36) according to claim 11, characterized in that, in the transport direction (3) of the strand (2), a winding device and/or a saw (34) is arranged behind the cold-forming device, which winding device and/or saw (34) is movable in the transport direction (3) of the strand (2).

14. The molding system (36) according to claim 13, characterized in that a cleaning device (35) for cleaning the outer surface of the strand (2) is arranged between the cold-forming device and the winding device and/or saw (34).

15. A method for annealing a steel strand (2) in an annealing furnace (1), having the following steps:

heating the strand (2) in a first heating device (9), and

advancing the strand (2) through the annealing furnace (1) in a transport direction (3) by means of a transport device (4, 5,6, 7),

cooling an outer surface (17) of the strand (2) in a first cooling device (13) behind the first heating device (9) in the transport direction (3), the first cooling device (13) having a gas guide (16), wherein gas flows over the outer surface (17) of the strand (2) with the aid of the gas guide (16) to cool the strand (2),

characterized in that the method further comprises the steps of:

cooling the outer surface (17) of the strand (2) in a second cooling device (14) in the transport direction (3), the second cooling device (14) comprising a contact element (25), the contact element (25) being engageable with the strand (2) during operation of the annealing furnace (1) in order to establish a thermal contact between the strand (2) and the contact element (25), wherein the contact element (25) comprises graphite and the gas guide of the first cooling device comprises a housing consisting of three sections, the second cooling device extends in a middle section of the housing and the contact element consists of four cheek plates, between which a gap is provided.

16. A method for producing steel strands (2) by cold-forming a steel tube blank into strands (2) and according to the method of claim 15.